Caulophyine A, a Rare Azapyrene Alkaloid from the Roots of Caulophyllum robustum.

A novel alkaloid caulophyine A (1) was isolated from the roots of Caulophyllum robustum Maxim., along with six known alkaloids 2-7. The structure of 1 was elucidated by extensive NMR and high resolution-time-of-flight (HR-TOF)-MS analyses, it is a rare nitrogen containing polycyclic aromatic hydrocarbon. The in vitro bioassays revealed that 2 presented remarkable cytotoxicity against A549 with an IC50 value of 3.83 µM in comparison with the positive control etoposide (IC50  = 11.63 µM). Compounds 1 and 2 also displayed weak Acetylcholinesterase (AChE) inhibitory activity with IC50 values of 123.03 and 80.74 µM respectively.